Excellent Rated 5 out of 5 stars

2 issues:

The css should not add margins on left/right side (this can be fixed by editing the css in the xpi of this extension in the firefox profiles folder)

The title of the tab should only show the contents of the first line of the md file (currently it is like '<title>=======loremipsum').

Great on Linux Rated 5 out of 5 stars

Very useful. No problems on Linux (Kubuntu). I did not have to tweak anything and it works perfect. Thank you!

The only md viewer addon available Rated 5 out of 5 stars

Works for most .md files. While it might not be perfect, I really admire the great act of filling the vacuum.
@developer
Kindly correct the errors mentioned by someone here. That makes this the one and only addon in its true sense.

Rated 5 out of 5 stars

5 stars, thanks!

This review is for a previous version of the add-on (1.6). 

Good but... Rated 4 out of 5 stars

but, This cant convert "`#include &amp;lt;functional&amp;gt;`" into "&amp;lt;code&amp;gt;#include &amp;amp;lt;functional&amp;amp;gt;&amp;lt;/code&amp;gt;"

日本人なので日本語で書きますが、&lt;や&gt;がエスケープされません。これを除けばとても便利なアドオンです。
UTF-8エンコードのテキストファイルを読み込んで見た結果、2バイトでも文字化けしませんし。

This review is for a previous version of the add-on (1.6). 

Very Good Rated 5 out of 5 stars

5 start for it's the only one I can find that fit me ^_^.

just notice the (for V1.5) in the comment below. Author has relased newer version on github, just follow "Add-on home page" link in the left panel.

For someone who want to update it yourself:
1. Download the xpi file, extract it to a folder
2. Download the latest marded.js from https://github.com/chjj/marked. It's in the lib folder
3. Replace the one in xpi with the latest one
4. Compressed the extracted files to zip and rename it with xpi, then install it.

This review is for a previous version of the add-on (1.3). 

Rated 4 out of 5 stars

conflict with add on "right to click"

This review is for a previous version of the add-on (1.3). 

(for v. 1.5) Nearly Perfect, but with visual flaw of extra script on page top. Rated 4 out of 5 stars

The visual flaw here : https://imageshack.com/i/1n3gn0j
.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Shown Script here :

window.oldSetTimeout=window.setTimeout;window.setTimeout=function(func,delay){return window.oldSetTimeout(function(){try{if(!document.documentElement.getAttribute('stopTimers')){if(typeof func=='string') {var nfunc = new Function(func); nfunc();} else func();}}catch(ex){}},delay);}; window.oldSetInterval=window.setInterval;window.setInterval=function(func,delay){return window.oldSetInterval(function(){try{if(!document.documentElement.getAttribute('stopTimers')){if(typeof func=='string') {var nfunc = new Function(func); nfunc();} else func();}}catch(ex){}},delay);};

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

This review is for a previous version of the add-on (1.3). 

Works as advertised Rated 4 out of 5 stars

It's simple (nothing's configurable) and gets the job done. The style sheet is fine. And it *can* read local files. So far, so good :)

The only drawback is that tab title is a hard-coded "Markdown Viewer" string. Among all the possibilities I could think of (file path, file name, first line, first title... or a combination of those) that's probably among the less useful.

This review is for a previous version of the add-on (1.3). 

Rated 4 out of 5 stars

Work on WinXP Pro SP3

This review is for a previous version of the add-on (1.3). 

Work on Linux Rated 5 out of 5 stars

I find it, and it`s work on Firefox 24 x Ubuntu 12.04.3 (GNU/Linux).

If there is not yet an existing RDF node for 'text/plain' add it, and add "md" as a file extension.

$ vi ~/.mozilla/firefox/*default/mimeTypes.rdf
......
<RDF:Description RDF:about="urn:mimetype:text/plain"
NC:value="text/plain"
NC:fileExtensions="md"
NC:description="Text Document">
<NC:handlerProp RDF:resource="urn:mimetype:handler:text/plain"/>
</RDF:Description>

----
Getting Markdown Viewer To Display HTML Formatted Markdown Content in Firefox Under Linux
- http://www.ryanchapin.com/fv-b-4-737/Getting-Markdown-Viewer-To-Display-HTML-Formatted-Markdown-Content-in-Firefox-Under-Linux.html

This review is for a previous version of the add-on (1.3). 

FAIL Rated 1 out of 5 stars

Cannot be used to view files on local filesystem -> primary use case FAIL.

This review is for a previous version of the add-on (1.3). 

Rated 5 out of 5 stars

Great little extension (and the workaround for Linux users for .md files https://addons.mozilla.org/en-US/firefox/addon/markdown-viewer/reviews/423328/ works nicely).

This review is for a previous version of the add-on (1.3). 

Rated 1 out of 5 stars

Neither of the two sane work-arounds actually work on Linux. Why should I rename my .md files to .mdown when .md is the standard? Is it really that hard to fix that bug?

This review is for a previous version of the add-on (1.3). 

It is, unfortunately.

Rated 5 out of 5 stars

It works like a charm!

Markdown files look very nice and I don't have to push anymore to Github to test whether my Markdown files are broken or not, saving some unnecessary commits!

This review is for a previous version of the add-on (1.3). 

Rated 5 out of 5 stars

great!! thank you for making.XD

This review is for a previous version of the add-on (1.2). 

Extension problem Rated 4 out of 5 stars

.mdown extension to file seems to be required, but .md file extension is common too, so it would be great to have support for it. Anyway, worked like a charm :)

This review is for a previous version of the add-on (1.2). 

Rated 5 out of 5 stars

I associated .md documents with Firefox, and now they are nicely formatted and easy to read. Piece of cake.

This review is for a previous version of the add-on (1.2). 

Linux tip and restart Rated 3 out of 5 stars

For linux users, try to add "md" to .mozilla/*.default/mimeTypes.rdf this line : <NC:fileExtensions>md</NC:fileExtensions>in text/plain section :)
Oh that would be nice if there no restart on install !

Thanks for this add-on it's very useful.

This review is for a previous version of the add-on (1.2). 

Rated 4 out of 5 stars

This plugin does not understand utf-8.I've written above before, but it actually works utf-8. I just needed to change the character encoding on firefox. (Toolbar -> View -> Character Encoding). Great Plugin. It'd be great if this plugin let me set the markdown file extension myself other than .mdown.

This review is for a previous version of the add-on (1.2).